Photoelectric conversion device, photoelectric conversion device material, photosensor and imaging device

ABSTRACT

A photoelectric conversion device comprising an electrically conductive film, an organic photoelectric conversion film, and a transparent electrically conductive film, wherein the organic photoelectric conversion film contains a compound represented by the following formula (1) and an n-type organic semiconductor: 
     
       
         
         
             
             
         
       
         
         
           
             wherein each of R 1  and R 2  independently represents a substituted aryl group, an unsubstituted aryl group, a substituted heteroaryl group or an unsubstituted heteroaryl group, each of R 3  to R 11  independently represents a hydrogen atom or a substituent provided that an acidic group is excluded, m represents 0 or 1, n represents an integer of 0 or more, R 1  and R 2 , R 3  and R 4 , R 3  and R 5 , R 5  and R 6 , R 6  and R 8 , R 7  and R 8 , R 7  and R 9 , or R 10  and R 11  may be combined each other to form a ring, and when n is an integer of 2 or more, out of a plurality of R 7 &#39;s and R 8 &#39;s, a pair of R 7 &#39;s, a pair of R 8 &#39;s, or a pair of R 7  and R 8  may be combined each other to form a ring.

CROSS-REFERENCE TO RELATED APPLICATION

This is a Divisional Application of U.S. application Ser. No. 12/891,897filed Sep. 28, 2010, which claims priority from Japanese PatentApplication No. 2009-225522 filed Sep. 29, 2009. The entire disclosuresof the prior applications are hereby incorporated by reference in theirentirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a photoelectric conversion device, aphotoelectric conversion device material, a photosensor and an imagingdevice.

2. Description of the Related Art

Conventional photosensors in general are a device fabricated by forminga photodiode (PD) in a semiconductor substrate such as silicon (Si). Asfor the solid-state imaging device, there is widely used a flatsolid-state imaging device where PD are two-dimensionally arrayed in asemiconductor substrate and a signal according to a signal chargegenerated by photoelectric conversion in each PD is read out through aCCD or CMOS circuit.

The method for realizing a color solid-state imaging device is generallyfabrication of a structure where on the light incident surface side ofthe flat solid-state imaging device, a color filter transmitting onlylight at a specific wavelength is disposed for color separation. Inparticular, a single-plate solid-state imaging device in which colorfilters transmitting blue (B) light, green (G) light and red (R) light,respectively, are regularly disposed on each of two-dimensionallyarrayed PD is well known as a system widely used at present in a digitalcamera and the like.

In this single-plate solid-state imaging device, since the color filtertransmits only light at a limited wavelength, light failed intransmitting through the color filter is not utilized and the lightutilization efficiency is bad. Also, in recent years, fabrication of amultipixel device is proceeding, and the pixel size and in turn, thearea of a photodiode part become small, which brings about problems ofreduction in the aperture ratio and reduction in the light collectionefficiency.

In order to solve these problems, a system of stacking, in thelongitudinal direction, photoelectric conversion parts capable ofdetecting light at different wavelengths has been proposed. As regardssuch a system, in so far as visible light is concerned, there aredisclosed, for example, a system utilizing wavelength dependency of theabsorption coefficient of Si, where a vertical stack structure is formedand colors are separated by the difference in the depth (Patent Document1), and a system where a first light-receiving part using an organicsemiconductor and second and third light-receiving parts each composedof Si are formed (Patent Document 2).

However, such a system is disadvantageous in that the color separationis poor, because the absorption range is overlapped among respectivelight-receiving parts in the depth direction of Si and the spectroscopicproperty is bad.

Also, development of a solid-state imaging device having a structurewhere an organic photoelectric conversion film is formed on a signalread-out substrate is proceeding.

In such a solid-state imaging device, it is a task particularly toenhance the photoelectric conversion efficiency or reduce the darkcurrent, and as a method for improving these properties, there aredisclosed, for example, introduction of a pn-junction (Non-PatentDocument 1) or introduction of a bulk heterojunction structure (PatentDocument 3) for the former and introduction of a blocking layer (PatentDocument 4) for the latter.

In the case of increasing the photoelectric conversion efficiency by theintroduction of pn-junction or bulk heterojunction structure, anincrease in the dark current often becomes a problem. Also, the degreeof improvement in the photoelectric conversion efficiency differsdepending on the combination of materials and in some cases, the ratioof photosignal amount/dark time noise does not increase from that beforeintroduction of such a structure. In employing the method above, whatmaterials are combined is important and in particular, when reduction inthe dark time noise is intended, this is difficult to achieve byconventionally reported combinations of materials.

As the literature describing a photoelectric conversion device using anorganic material, Patent Documents 5 to 7, Non-Patent Documents 2 and 3,and the like are also known.

Patent Document 5 describes a device using an organic photoelectricconversion film containing fullerenes, but it is impossible only byfullerenes to satisfy all of the above-described high photoelectricconversion efficiency, low dark current and high light absorption.

Patent Document 6 describes a heterocyclic compound containingthiophene, furan or pyrrole, and Patent Document 7 and Non-PatentDocuments 2 and 3 describe a solar cell by an organic photoelectricconversion device using a thiophene derivative and a fullerenederivative.

[Patent Document 1] U.S. Pat. No. 5,965,875 [Patent Document 2]JP-A-2003-332551 (the term “JP-A” as used herein means an “unexaminedpublished Japanese patent application”) [Patent Document 3]JP-A-2002-076391 [Patent Document 4] JP-A-5-129576 [Patent Document 5]JP-A-2007-123707 [Patent Document 6] JP-A-2005-132914 [Patent Document7] JP-A-2007-091714 [Non-Patent Document 1] Appl. Phys. Lett., 1986, 48,183 [Non-Patent Document 2] J. Am. Chem. Soc., 2006, 128, 3459[Non-Patent Document 3] Chem. Commun., 2008, 48, 6489

SUMMARY OF THE INVENTION

However, the devices of Patent Documents 5 to 7 and Non-Patent Documents2 and 3 are a device aiming at use as a solar cell, and neitherdisclosure about dark current reduction and the like is found norapplication and the like to a photoelectric conversion device for use inan imaging device is referred to.

An object of the present invention is to provide a photoelectricconversion device using an organic photoelectric conversion film,particularly a photoelectric conversion device excellent in thephotoelectric conversion efficiency, and a solid-state imaging device.

In an organic photoelectric conversion device, for realizing high lightabsorptivity, high photoelectric conversion efficiency and low darkcurrent, the organic photoelectric conversion film used preferablysatisfies the following requirements.

1. The molar extinction coefficient of the dye needs to be high.

2. In terms of high efficiency, the signal charge after dissociation ofan exciton needs to be swiftly transmitted to both electrodes withoutloss. High mobility and high charge transportability with a small numberof carrier trapping sites are necessary.

3. In terms of high photoelectric conversion efficiency, it is preferredthat the exciton stabilizing energy is small and the exciton can beswiftly dissociated by the effect of an externally applied electricfield or an electric field generated in the inside by pn-junction or thelike (high exciton dissociation efficiency).

4. In order to reduce as much the carrier generated in the inside atdark time as possible, it is preferred to select a film structure ormaterial that allows little presence of an intermediate level in theinside or impurities working out to one of causes thereof.

5. In the case of stacking a plurality of layers, an energy levelmatching the adjacent layer is required and if an energetic barrier isformed, this inhibits charge transport.

In the case of forming the organic photoelectric conversion film by avapor deposition method, the decomposition temperature is preferablyhigher than the temperature allowing for vapor deposition, because thethermal decomposition during vapor deposition can be suppressed. Thecoating method is advantageous in that the film can be formed withoutsubjecting to limitation by the decomposition above and a low cost canbe realized, but film formation by a vapor deposition method ispreferred because uniform film formation is facilitated and possiblemixing of impurities can be reduced.

As a result of intensive studies, the present inventors have found ahigh-absorption material capable of realizing high photoelectricconversion efficiency and low dark current.

According to the studies by the present inventors, it has been foundthat when a compound represented by the following formula (1) and ann-type semiconductor are used in combination, a photoelectric conversiondevice excellent in the photoelectric conversion efficiency is obtained.Also, it has been found that out of the compounds represented by thefollowing formula (1), a compound represented by the following formula(4) and a compound represented by formula (5) are a novel compounduseful as a photoelectric conversion material.

That is, the above-described object can be attained by the followingtechniques.

[1] A photoelectric conversion device comprising an electricallyconductive film, an organic photoelectric conversion film, and atransparent electrically conductive film, wherein the organicphotoelectric conversion film contains a compound represented by thefollowing formula (1) and an n-type organic semiconductor:

wherein each of R₁ and R₂ independently represents a substituted arylgroup, an unsubstituted aryl group, a substituted heteroaryl group or anunsubstituted heteroaryl group, each of R₃ to R₁₁ independentlyrepresents a hydrogen atom or a substituent provided that an acidicgroup is excluded, m represents 0 or 1, n represents an integer of 0 ormore, R₁ and R₂, R₃ and R₄, R₃ and R₅, R₅ and R₆, R₆ and R₈, R₇ and R₈,R₇ and R₉, or R₁₀ and R₁₁ may be combined each other to form a ring, andwhen n is an integer of 2 or more, out of a plurality of R₇'s and R₈'s,a pair of R₇'s, a pair of R₈'s, or a pair of R₇ and R₈ may be combinedeach other to form a ring.

[2] The photoelectric conversion device according to the above [1],wherein the compound represented by formula (1) is a compoundrepresented by the following formula (2):

wherein R₁ to R₉, m and n have the same meanings as above, each of R₁₁and R₁₂ independently represents a hydrogen atom or a substituent, andR₁₁ and R₁₂ may be combined each other to form a ring.

[3] The photoelectric conversion device according to the above [2],wherein the compound represented by formula (2) is a compoundrepresented by the following formula (3):

wherein R₁ to R₉, m and n have the same meanings as above, each of R₁₃and R₁₄ independently represents a hydrogen atom or a substituent, andR₁₃ and R₁₄ may be combined each other to form a ring.

[4] The photoelectric conversion device according to the above [3],wherein the compound represented by formula (3) is a compoundrepresented by the following formula (4):

wherein R₁ to R₉, m and n have the same meanings as above, each of R₁₅to R₁₈ independently represents a hydrogen atom or a substituent, andR₁₅ and R₁₆, R₁₆ and R₁₇, or R₁₇ and R₁₈ may be combined each other toform a ring.

[5] The photoelectric conversion device according to the above [3],wherein the compound represented by formula (3) is a compoundrepresented by the following formula (5):

wherein R₁ to R₉, m and n have the same meanings as above, each of R₁₅and R₁₈ to R₂₂ independently represents a hydrogen atom or asubstituent, and R₁₅ and R₁₉, R₁₉ and R₂₀, R₂₀ and R₂₁, R₂₁ and R₂₂, orR₂₂ and R₁₈ may be combined each other to form a ring.

[6] The photoelectric conversion device according to any one of theabove [1] to [5], wherein the n-type organic semiconductor is afullerene or a fullerene derivative.[7] The photoelectric conversion device according to any one of theabove [1] to [6], further comprising an electron blocking film.[8] The photoelectric conversion device according to the above [7],wherein the electrically conductive film, the electron blocking film,the organic photoelectric conversion film and the transparentelectrically conductive film are stacked in this order or theelectrically conductive film, the organic photoelectric conversion film,the electron blocking film and the transparent electrically conductivefilm are stacked in this order.[9] The photoelectric conversion device according to any one of theabove [1] to [8], wherein n in formula (1) represents any integer of 0to 3.[10] The photoelectric conversion device according to any one of theabove [6] to [9], wherein the volume ratio of the fullerene or fullerenederivative to the compound represented by formula (1) (fullerene orfullerene derivative/compound represented by formula (1)×100(%)) is 50%or more.[11] The photoelectric conversion device according to any one of theabove [1] to [10], wherein light is incident on the organicphotoelectric conversion film through the transparent electricallyconductive film.[12] The photoelectric conversion device according to any one of theabove [1] to [11], wherein the transparent electrically conductive filmcomprises a transparent electrically conductive oxide.[13] The photoelectric conversion device according to any one of theabove [1] to [12], wherein the transparent electrically conductive filmis stacked directly on the organic photoelectric conversion film.[14] A use method of the photoelectric conversion device according toany one of the above [1] to [13], with the electrically conductive filmand the transparent electrically conductive film defining a pair ofelectrodes, the method comprising applying an electric field of 1×10⁻⁴to 1×10⁷ V/cm between the pair of electrodes.[15] A photosensor comprising the photoelectric conversion deviceaccording to any one of the above [1] to [13].[16] An imaging device containing the photoelectric conversion deviceaccording to any one of the above [1] to [13].[17] A compound represented by the following formula (4):

wherein each of R₁ and R₂ independently represents a substituted arylgroup, an unsubstituted aryl group, a substituted heteroaryl group or anunsubstituted heteroaryl group, each of R₃ to R₉ and R₁₅ to R₁₈independently represents a hydrogen atom or a substituent, m represents0 or 1, and n represents an integer of 0 or more,

R₁ and R₂, R₃ and R₄, R₃ and R₅, R₅ and R₆, R₆ and R₈, R₇ and R₈, R₇ andR₉, R₁₅ and R₁₆, R₁₆ and R₁₇, or R₁₇ and R₁₈ may be combined each otherto form a ring, and when n is an integer of 2 or more, out of aplurality of R₇'s and R₈'s, a pair of R₇'s, a pair of R₈'s, or a pair ofR₇ and R₈ may be combined each other to form a ring.

[18] A compound represented by the following formula (5):

wherein each of R₁ and R₂ independently represents a substituted arylgroup, an unsubstituted aryl group, a substituted heteroaryl group or anunsubstituted heteroaryl group, each of R₃ to R₉, R₁₅ and R₁₈ to R₂₂independently represents a hydrogen atom or a substituent, m represents0 or 1, and n represents an integer of 0 or more,

R₁ and R₂, R₃ and R₄, R₃ and R₅, R₅ and R₆, R₆ and R₈, R₇ and R₈, R₇ andR₉, R₁₅ and R₁₉, R₁₉ and R₂₀, R₂₀ and R₂₁, R₂₁ and R₂₂, or R₂₂ and R₁₈may be combined each other to form a ring, and when n is an integer of 2or more, out of a plurality of R₇'s and R₈'s, a pair of R₇'s, a pair ofR₈'s, or a pair of R₇ and R₈ may be combined each other to form a ring.

[19] A photoelectric conversion device comprising an electricallyconductive film, an organic photoelectric conversion film, and atransparent electrically conductive film, wherein the organicphotoelectric conversion film contains the compound according to theabove [17] or [18].[20] A photosensor comprising the photoelectric conversion deviceaccording to the above [19].[21] An imaging device containing the photoelectric conversion deviceaccording to the above [19].

According to the present invention, an organic photoelectric conversiondevice and a solid-state imaging device, which are excellent in thephotoelectric conversion efficiency, can be provided.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A and FIG. 1B each is a schematic cross-sectional view showing oneconfiguration example of a photoelectric conversion device.

FIG. 2 is a schematic cross-sectional view of one pixel portion of animaging device.

FIG. 3 is a schematic cross-sectional view of one pixel portion of animaging device in another configuration example.

FIG. 4 is a schematic cross-sectional view of one pixel portion of animaging device in another configuration example.

FIG. 5 is a schematic partial surface view of an imaging device inanother configuration example.

FIG. 6 is a schematic cross-sectional view cut along the X-X line of theimaging device shown in FIG. 5.

DESCRIPTION OF REFERENCE NUMERALS AND SIGNS

-   11 Lower electrode (electrically conductive film)-   12 Photoelectric conversion layer (photoelectric conversion film)-   15 Upper electrode (transparent electrically conductive film)-   16A Electron blocking layer-   16B Hole blocking layer-   100, 200, 300, 400 Imaging Device

DETAILED DESCRIPTION OF THE INVENTION

The embodiments of the photoelectric conversion device according to thepresent invention are described below.

[Substituent W]

The substituent W is described below.

The substituent W includes a halogen atom, an alkyl group (including acycloalkyl group, a bicycloalkyl group and a tricycloalkyl group), analkenyl group (including a cycloalkenyl group and a bicycloalkenylgroup), an alkynyl group, an aryl group, a heterocyclic group (may alsobe called a hetero-ring group), a cyano group, a hydroxy group, a nitrogroup, an alkoxy group, an aryloxy group, a silyloxy group, aheterocyclic oxy group, an acyloxy group, a carbamoyloxy group, analkoxycarbonyloxy group, an aryloxycarbonyloxy group, an amino group(including an anilino group), an ammonio group, an acylamino group, anaminocarbonylamino group, an alkoxycarbonylamino group, anaryloxycarbonylamino group, a sulfamoylamino group, analkylsulfonylamino group, an arylsulfonylamino group, a mercapto group,an alkylthio group, an arylthio group, a heterocyclic thio group, asulfamoyl group, an alkylsulfinyl group, an arylsulfinyl group, analkylsulfonyl group, an arylsulfonyl group, an acyl group, anaryloxycarbonyl group, an alkoxycarbonyl group, an alkylcarbonyl group,a carbamoyl group, an arylazo group, a heterocyclic azo group, an imidogroup, a phosphino group, a phosphinyl group, a phosphinyloxy group, aphosphinyl-amino group, a phosphono group, a silyl group, a hydrazinogroup, a ureido group and other known substituents.

More preferably, W represents, for example, the following (1) to (17):

(1) a halogen atom,

such as fluorine atom, chlorine atom, bromine atom and iodine atom;

(2) an alkyl group,

a linear, branched or cyclic alkyl group:

(2-a) an alkyl group,

preferably an alkyl group having a carbon number of 1 to 30 (e.g.,methyl, ethyl, n-propyl, isopropyl, tert-butyl, n-octyl, eicosyl,2-chloroethyl, 2-cyanoethyl, 2-ethylhexyl), and

(2-b) a cycloalkyl group,

preferably a substituted or unsubstituted cycloalkyl group having acarbon number of 3 to 30 (e.g., cyclohexyl, cyclopentyl,4-n-dodecylcyclohexyl);

(3) an alkenyl group,

a linear, branched or cyclic alkenyl group having a carbon number of 2to 30 (e.g., vinyl, allyl, styryl);

(4) an alkynyl group,

preferably an alkynyl group having a carbon number of 2 to 30 (e.g.,ethynyl, propargyl, trimethylsilylethynyl);

(5) an aryl group,

preferably an aryl group having a carbon number of 6 to 30 (e.g.,phenyl, p-tolyl, naphthyl, m-chlorophenyl, o-hexadecanoylaminophenyl,ferrocenyl);

(6) a heterocyclic group,

preferably a monovalent group obtained by removing one hydrogen atomfrom a 5- or 6-membered aromatic or non-aromatic heterocyclic compound,more preferably a 5- or 6-membered aromatic heterocyclic group having acarbon number of 2 to 50 (e.g., 2-furyl, 2-thienyl, 2-pyrimidinyl,2-benzothiazolyl; the heterocyclic group may also be a cationicheterocyclic group such as 1-methyl-2-pyridinio and1-methyl-2-quinolinio);

(7) an alkoxy group,

preferably an alkoxy group having a carbon number of 1 to 30 (e.g.,methoxy, ethoxy, isopropoxy, tert-butoxy, n-octyloxy, 2-methoxyethoxy);

(8) an aryloxy group,

preferably an aryloxy group having a carbon number of 6 to 30 (e.g.,phenoxy, 2-methylphenoxy, 4-tert-butylphenoxy, 3-nitrophenoxy,2-tetradecanoylaminophenoxy);

(9) an amino group,

preferably an amino group, an alkylamino group having a carbon number of1 to 30, or an anilino group having a carbon number of 6 to 30 (e.g.,amino, methylamino, dimethylamino, anilino, N-methyl-anilino anddiphenylamino);

(10) an alkylthio group,

preferably an alkylthio group having a carbon number of 1 to 30 (e.g.,methylthio, ethylthio, n-hexadecylthio);

(11) an arylthio group,

preferably an arylthio group having a carbon number of 6 to 30 (e.g.,phenylthio, p-chlorophenylthio, m-methoxyphenylthio);

(12) a heterocyclic thio group,

preferably a substituted or unsubstituted heterocyclic thio group havinga carbon number of 2 to 30 (e.g., 2-benzothiazolylthio,1-phenyltetrazol-5-ylthio);

(13) an alkyl- or aryl-sulfinyl group,

preferably a substituted or unsubstituted alkylsulfinyl group having acarbon number of 1 to 30, or a substituted or unsubstituted arylsulfinylgroup having a carbon number of 6 to 30 (e.g., methylsulfinyl,ethylsulfinyl, phenylsulfinyl and p-methylphenylsulfinyl);

(14) an alkyl- or aryl-sulfonyl group,

preferably an alkylsulfonyl group having a carbon number of 1 to 30, oran arylsulfonyl group having a carbon number of 6 to 30 (e.g.,methylsulfonyl, ethylsulfonyl, phenylsulfonyl andp-methylphenylsulfonyl);

(15) an acyl group,

preferably a formyl group, an alkylcarbonyl group having a carbon numberof 2 to 30, an arylcarbonyl group having a carbon number of 7 to 30, ora heterocyclic carbonyl group having a carbon number of 4 to 30 andbeing bonded to a carbonyl group through a carbon atom (e.g., acetyl,pivaloyl, 2-chloroacetyl, stearoyl, benzoyl, p-n-octyloxyphenylcarbonyl,2-pyridylcarbonyl and 2-furylcarbonyl);

(16) a phosphino group,

preferably a phosphino group having a carbon number of 2 to 30 (e.g.,dimethylphosphino, diphenylphosphino, methylphenoxyphosphino); and

(17) a silyl group,

preferably a silyl group having a carbon number of 3 to 30 (e.g.,trimethylsilyl, triethylsilyl, triisopropylsilyl,tert-butyldimethylsilyl, phenyldimethylsilyl).

[Ring R]

The ring R includes an aromatic or non-aromatic hydrocarbon ring, aheterocyclic ring, and a polycyclic condensed ring formed by furthercombining these rings. Examples thereof include a benzene ring, anaphthalene ring, an anthracene ring, a phenanthrene ring, a fluorenering, a triphenylene ring, a naphthacene ring, a biphenyl ring, apyrrole ring, a furan ring, a thiophene ring, an imidazole ring, anoxazole ring, a thiazole ring, a pyridine ring, a pyrazine ring, apyrimidine ring, a pyridazine ring, an indolizine ring, an indole ring,a benzofuran ring, a benzothiophene ring, an isobenzofuran ring, aquinolidine ring, a quinoline ring, a phthalazine ring, a naphthylidinering, a quinoxaline ring, a quinoxazoline ring, an isoquinoline ring, acarbazole ring, a phenanthridine ring, an acridine ring, aphenanthroline ring, a thianthrene ring, a chromene ring, a xanthenering, a phenoxathiine ring, a phenothiazine ring and a phenazine ring.

[Photoelectric Conversion Device]

The photoelectric conversion device of the present invention comprisesan electrically conductive film, an organic photoelectric conversionfilm and a transparent electrically conductive film. In a preferredembodiment, the photoelectric conversion device has an electron blockinglayer, in addition to an electrically conductive film, an organicphotoelectric conversion film and a transparent electrically conductivefilm, and this embodiment includes an embodiment where the electricallyconductive film, the electron blocking film, the organic photoelectricconversion film and the transparent electrically conductive film arestacked in this order, and an embodiment where the electricallyconductive film, the organic photoelectric conversion film, the electronblocking film and the transparent electrically conductive film arestacked in this order.

The organic photoelectric conversion film contains a compoundrepresented by the following formula (1) and an n-type semiconductor.

wherein each of R₁ and R₂ independently represents a substituted arylgroup, an unsubstituted aryl group, a substituted heteroaryl group or anunsubstituted heteroaryl group, each of R₃ to R₁ independentlyrepresents a hydrogen atom or a substituent provided that an acidicgroup is excluded, m represents 0 or 1, n represents an integer of 0 ormore, R₁ and R₂, R₃ and R₄, R₃ and R₅, R₅ and R₆, R₆ and R₈, R₇ and R₈,R₇ and R₉, or R₁₀ and R₁₁ may be combined with each other to form aring, and when n is an integer of 2 or more, out of a plurality of R₇'sand R₈'s, a pair of R₇'s, a pair of R₈'s, or a pair of R₇ and R₈ may becombined with each other to form a ring.

The photoelectric conversion device of the present invention contains acompound represented by formula (1) and an n-type organic semiconductorin the photoelectric conversion film, whereby a device with highphotoelectric conversion efficiency is obtained. The operation mechanismthereof is not clearly know, but it is presumed that thanks to a highmolar extinction coefficient of the compound and production of a highlyefficient charge separation state or highly efficient charge transportpath by the formation of a bulk heterojunction structure with an n-typeorganic semiconductor (preferably a fullerene or a fullerenederivative), the photoelectric conversion efficiency can be enhanced.

Preferred embodiments of the photoelectric conversion device accordingto the present invention are described below.

FIGS. 1A and 1B shows a configuration example of the photoelectricconversion device of the present invention.

The photoelectric conversion device 10 a shown in FIG. 1A has aconfiguration where an electrically conductive film (hereinafterreferred to as a lower electrode) 11 functioning as a lower electrode,an electron blocking layer 16A (electron blocking film) formed on thelower electrode 11, a photoelectric conversion layer 12 (organicphotoelectric conversion film) formed on the electron blocking layer16A, and a transparent electrically conductive film (hereinafterreferred to as an upper electrode) 15 functioning as an upper electrodeare stacked.

FIG. 1B shows another configuration example of the photoelectricconversion device. The photoelectric conversion device 10 b shown inFIG. 1B has a configuration where an electron blocking layer 16A(electron blocking film), a photoelectric conversion layer 12 (organicphotoelectric conversion film), a hole blocking layer 16B and an upperelectrode 15 are stacked in this order on a lower electrode 11.Incidentally, in FIG. 1A and FIG. 1B, the order of stacking an electronblocking layer, a photoelectric conversion layer and a hole blockinglayer may be reversed according to usage or properties.

In these cases, light is preferably incident on the organicphotoelectric conversion film from above the upper electrode(transparent electrically conductive film).

Also, in using such a photoelectric conversion device, an electric fieldcan be applied. In this case, the electrically conductive film and thetransparent electrically conductive film define a pair of electrodes,and an electric field of, for example, 1×10⁻⁴ to 1×10⁷ V/cm can beapplied between the pair of electrodes.

The elements constituting the photoelectric conversion device accordingto this embodiment are described below.

(Electrode)

Each of the electrodes (the upper electrode (transparent electricallyconductive film) 15 and the lower electrode (electrically conductivefilm) 11) is composed of an electrically conductive material. Examplesof the electrically conductive material which can be used include ametal, an alloy, a metal oxide, an electroconductive compound, and amixture thereof.

Light is incident from the upper electrode 15 and therefore, the upperelectrode 15 needs to be sufficiently transparent to light that is to bedetected. Specific examples thereof include an electrically conductivemetal oxide such as tin oxide doped with antimony or fluorine (ATO,FTO), tin oxide, zinc oxide, indium oxide, indium tin oxide (ITO) andindium zinc oxide (IZO); a thin metal film such as gold, silver,chromium and nickel; a mixture or laminate of such a metal and such anelectrically conductive metal oxide; an inorganic electricallyconductive substance such as copper iodide and copper sulfide; anorganic electrically conductive material such as polyaniline,polythiophene and polypyrrole; and a laminate of such a material andITO. Among these, an electrically conductive metal oxide is preferred inview of high electrical conductivity, transparency and the like. Theupper electrode 15 is deposited on the organic photoelectric conversionlayer 12 and therefore, is preferably deposited by a method causing nodeterioration of the properties of the organic photoelectric conversionlayer 12. Also, the upper electrode 15 is preferably composed of atransparent electrically conductive oxide.

The lower electrode 11 includes, according to usage, a case wheretransparency is imparted, a case where, conversely, a material capableof reflecting light is used without imparting transparency, and thelike. Specific examples thereof include an electrically conductive metaloxide such as tin oxide doped with antimony or fluorine (ATO, FTO), tinoxide, zinc oxide, indium oxide, indium tin oxide (ITO) and indium zincoxide (IZO); a metal such as gold, silver, chromium, nickel, titanium,tungsten and aluminum; an electrically conductive compound such as oxideand nitride of the metal (for example, titanium nitride (TiN)); amixture or laminate of such a metal and such an electrically conductivemetal oxide; an inorganic electrically conductive substance such ascopper iodide and copper sulfide; an organic electrically conductivematerial such as polyaniline, polythiophene and polypyrrole; and alaminate of such a material and ITO or titanium nitride.

The method for forming the electrode is not particularly limited and maybe appropriately selected by taking into consideration the aptitude forthe electrode material. Specifically, the electrode can be formed, forexample, by a wet system such as printing and coating, a physical systemsuch as vacuum deposition, sputtering and ion plating, or a chemicalsystem such as CVD and plasma CVD.

In the case where the material of the electrode is ITO, the electrodecan be formed by a method such as electron beam method, sputteringmethod, resistance heating deposition method, chemical reaction method(e.g., sol-gel method) and coating of a dispersion of indium tin oxide.The film produced using ITO may be further subjected to, for example, aUV-ozone treatment or a plasma treatment. In the case where the materialof the electrode is TiN, various methods including a reactive sputteringmethod are used, and the film formed can be further subjected to aUV-ozone treatment, a plasma treatment or the like.

The upper electrode 15 is preferably produced in a plasma-free state.When the upper electrode 15 is produced in a plasma-free state, theeffect of plasma on the substrate can be reduced and good photoelectricconversion properties can be obtained. Here, the plasma-free state meansa state where plasma is not generated during deposition of the upperelectrode 15 or where the distance from a plasma source to the substrateis 2 cm or more, preferably 10 cm or more, more preferably 20 cm ormore, and the amount of plasma reaching the substrate is reduced.

Examples of the apparatus generating no plasma during deposition of theupper electrode 15 include an electron beam deposition apparatus (EBdeposition apparatus) and a pulsed laser deposition apparatus. As forthe EB deposition apparatus or pulsed laser deposition apparatus,apparatuses described, for example, in Yutaka Sawada (supervisor), TomeiDoden Maku no Shin Tenkai (New Development of Transparent ConductiveFilm), CMC (1999), Yutaka Sawada (supervisor), Tomei Doden Maku no ShinTenkai II (New Development of Transparent Conductive Film II), CMC(2002), Tomei Doden Maku no Gijutsu (Technology of TransparentConductive Film), JSPS, Ohmsha (1999), and references cited therein canbe used. In the following, the method of depositing the transparentelectrode film by using an EB deposition apparatus is referred to as anEB deposition method, and the method of depositing the transparentelectrode film by using a pulsed laser deposition apparatus is referredto as a pulsed laser deposition method.

As for the apparatus capable of realizing a state where the distancefrom a plasma source to the substrate is 2 cm or more and the amount ofplasma reaching the substrate is reduced (hereinafter referred to as a“plasma-free deposition apparatus”), an opposed-target sputteringapparatus, an arc plasma deposition method and the like are considered,and examples of such an apparatuses which can be used include thosedescribed in Yutaka Sawada (supervisor), Tomei Doden Maku no Shin Tenkai(New Development of Transparent Conductive Film), CMC (1999), YutakaSawada (supervisor), Tomei Doden Maku no Shin Tenkai II (Development ofTransparent Conductive Film II), CMC (2002), Tomei Doden Maku no Gijutsu(Technology of Transparent Conductive Film), JSPS, Ohmsha (1999), andreferences cited therein.

In the case where the upper electrode 15 is a transparent electricallyconductive film such as TCO, a DC short or an increase of leak currentsometimes occurs. One of causes thereof is considered because finecracks introduced into the photoelectric conversion layer 12 arecoveraged by a dense film such as TCO to increase the conduction withthe first electrode film 11 on the opposite side. Therefore, in the caseof an electrode having relatively poor film quality such as Al, the leakcurrent hardly increases. The increase of leak current can be greatlysuppressed by controlling the film thickness of the upper electrode 15with respect to the film thickness (that is, the crack depth) of thephotoelectric conversion layer 12. The thickness of the upper electrode15 is preferably ⅕ or less, more preferably 1/10 or less, of thethickness of the photoelectric conversion layer 12.

Usually, when the thickness of the electrically conductive film is madesmaller than a certain range, an abrupt increase of the resistance valueis incurred, but in the solid-state imaging device where thephotoelectric conversion device according to this embodiment isincorporated, the sheet resistance may be, preferably, from 100 to10,000 Ω/sq. and the latitude as to in which range the film thicknesscan be reduced is large. Also, as the thickness of the upper electrode(transparent electrically conductive film) 15 is smaller, the quantityof light absorbed is reduced and the light transmittance is generallyincreased. The increase of light transmittance brings about an increaseof light absorption in the photoelectric conversion layer 12 and anincrease of photoelectric conversion performance, and this is verypreferred. Considering the suppression of leak current and the increaseof resistance value of thin film as well as the increase oftransmittance, which are associated with reduction in the filmthickness, the thickness of the upper electrode 15 is preferably from 5to 100 nm, more preferably from 5 to 20 nm.

(Photoelectric Conversion Layer)

The photoelectric conversion layer contains a compound represented bythe following formula (1):

wherein each of R₁ and R₂ independently represents a substituted arylgroup, an unsubstituted aryl group, a substituted heteroaryl group or anunsubstituted heteroaryl group, each of R₃ to R₁₁ independentlyrepresents a hydrogen atom or a substituent provided that an acidicgroup is excluded, m represents 0 or 1, n represents an integer of 0 ormore,

R₁ and R₂, R₃ and R₄, R₃ and R₅, R₅ and R₆, R₆ and R₈, R₇ and R₈, R₇ andR₉, or R₁₀ and R₁₁ may combine with each other to form a ring, and whenn is an integer of 2 or more, out of a plurality of R₇'s and R₈'s, apair of R₇'s, a pair of R₈'s, or a pair of R₇ and R₈ may combine witheach other to form a ring.

m represents 0 or 1 and is preferably 0.

n represents an integer of 0 or more and preferably represents anyinteger of 0 to 3. When n becomes large, the absorption wavelengthregion is allowed to reside on a long wavelength side, but from thestandpoint of having appropriate absorption in the visible region, n ismore preferably 0, 1 or 2.

Each of R₁ and R₂ independently represents a substituted orunsubstituted aryl group or a substituted or unsubstituted heteroarylgroup.

The aryl group represented by R₁ and R₂ is preferably an aryl grouphaving a carbon number of 6 to 30, more preferably an aryl group havinga carbon number of 6 to 20. Specific examples of the aryl group includea phenyl group, a naphthyl group, a biphenylyl group, a terphenyl group,an anthryl group and a fluorenyl group.

The substituent of the substituted aryl group in R₁ and R₂ is preferablyan alkyl group (e.g., methyl, ethyl, tert-butyl), an alkoxy group (e.g.,methoxy, ethoxy, isopropoxy), an aryl group (e.g., phenyl, naphthyl,phenanthryl, anthryl) or a heteroaryl group (e.g., thienyl, furanyl,pyridyl, carbazolyl).

The aryl group or substituted aryl group represented by R₁ and R₂ ispreferably a phenyl group, an alkyl-substituted phenyl group, a biphenylgroup, a naphthyl group, a phenanthryl group, an anthryl group or asubstituted fluorenyl group (preferably a 9,9′-dimethyl-2-fluorenylgroup).

In the case where each of R₁ and R₂ is a heteroaryl group, theheteroaryl group is preferably a heteroaryl group composed of a 5-, 6-or 7-membered ring or a condensed ring thereof. Examples of theheteroatom contained in the heteroaryl group include an oxygen atom, asulfur atom and a nitrogen atom. Specific examples of the ringconstituting the heteroaryl group include a furan ring, a thiophenering, a pyrrole ring, a pyrroline ring, a pyrrolidine ring, an oxazolering, an isoxazole ring, a thiazole ring, an isothiazole ring, animidazole ring, an imidazoline ring, an imidazolidine ring, a pyrazolering, a pyrazoline ring, a pyrazolidine ring, a triazole ring, afurazane ring, a tetrazole ring, a pyrane ring, a thiine ring, apyridine ring, a piperidine ring, an oxazine ring, a morpholine ring, athiazine ring, a pyridazine ring, a pyrimidine ring, a pyrazine ring, apiperazine ring and a triazine ring.

Examples of the condensed ring include a benzofuran ring, anisobenzofuran ring, a benzothiophene ring, an indole ring, an indolinering, an isoindole ring, a benzoxazole ring, a benzothiazole ring, anindazole ring, a benzimidazole ring, a quinoline ring, an isoquinolinering, a cinnoline ring, a phthalazine ring, a quinazoline ring, aquinoxaline ring, a dibenzofuran ring, a carbazole ring, a xanthenering, an acridine ring, a phenanthridine ring, a phenanthroline ring, aphenazine ring, a phenoxazine ring, a thianthrene ring, an indolizinering, a quinolidine ring, a quinuclidine ring, a naphthylidine ring, apurine ring and a pteridine ring.

The substituent of the substituted heteroaryl group in R₁ and R₂ ispreferably an alkyl group (e.g., methyl, ethyl, tert-butyl), an alkoxygroup (e.g., methoxy, ethoxy, isopropoxy), an aryl group (e.g., phenyl,naphthyl, phenanthryl, anthryl) or a heteroaryl group (e.g., thienyl,furanyl, pyridyl, carbazolyl).

The heteroaryl group or substituted heteroaryl group represented by R₁and R₂ is preferably a thienyl group, a substituted thienyl group, afuranyl group or a carbazolyl group.

Each of R₁ and R₂ is preferably a substituted or unsubstituted phenylgroup, a substituted or unsubstituted naphthyl group, a substituted orunsubstituted biphenyl group, a substituted or unsubstituted anthrylgroup, a substituted or unsubstituted fluorenyl group, or a groupcomposed of a ring selected from a furan ring, a thiophene ring, abenzofuran ring, an isobenzofuran ring, a benzothiophene ring and acarbazole ring.

In formula (1), each of R₃ to R₁₁ independently represents a hydrogenatom or a substituent provided that an acidic group is excluded. In thecase where each of R₃ to R₁₁ represents a substituent, examples of thesubstituent include the substituent W. The substituent represented by R₃to R₁₁ is preferably a halogen atom, an alkyl group, an alkenyl group,an alkynyl group, a cycloalkyl group, an alkoxy group, an alkylcarbonylgroup, an alkylthio group, an aryl group, a heteroaryl group or amercapto group, more preferably a halogen atom (e.g., fluorine,chlorine, bromine, iodine), an alkyl group having a carbon number of 1to 20 (preferably a carbon number of 1 to 10), an alkenyl group having acarbon number of 2 to 20 (preferably a carbon number of 2 to 10), analkynyl group having a carbon number of 2 to 20 (preferably a carbonnumber of 2 to 10), a cycloalkyl group having a carbon number of 3 to 8(preferably a carbon number of 4 to 6), an alkoxy group having a carbonnumber of 1 to 20 (preferably a carbon number of 1 to 10), an alkylthiogroup having a carbon number of 1 to 20 (preferably a carbon number of 1to 10), an aryl group having a carbon number of 6 to 30 (preferably acarbon number of 6 to 20), a heteroaryl group composed of a 5-, 6- or7-membered ring or a condensed ring thereof, containing at least any oneof oxygen atom, sulfur atom and nitrogen atom as a heteroatom, or amercapto group.

The above-described alkyl group, alkenyl group and alkynyl group may beeither branched or linear.

In the case where each of R₃ to R₈ is a substituent, the substituent ismore preferably an alkyl group having a carbon number of 1 to 10, analkenyl group having a carbon number of 2 to 10, an alkoxy group havinga carbon number of 1 to 10, or an alkylthio group having a carbon numberof 1 to 10.

Specifically, the alkyl group is preferably a methyl group, an ethylgroup, a propyl group, an i-propyl group or a tert-butyl group.

The alkenyl group is preferably a vinyl group (CH₂═CH—) or an allylgroup (CH₂═CHCH₂—).

In the case where R₉ is a substituent, the substituent is morepreferably an alkyl group having a carbon number of 1 to 10. R₉ ispreferably a hydrogen atom, a methyl group or an ethyl group, morepreferably a hydrogen atom.

In the case where each of R₃ to R₁₁ represents a substituent, thesubstituent may have a further substituent. Examples of the furthersubstituent include the substituent W. Among these, a halogen atom, analkyl group (preferably having a carbon number of 1 to 6), and an arylgroup (preferably having a carbon number of 6 to 10) are preferred.

R₁ and R₂, R₃ and R₄, R₃ and R₅, R₅ and R₆, R₆ and R₈, R₇ and R₈, R₇ andR₉, or R₁₀ and R₁₁ may combine with each other to form a ring, and whenn is an integer of 2 or more, out of a plurality of R₇'s and R₈'s, apair of R₇'s, a pair of R₈'s, or a pair of R₇ and R₈ may combine witheach other to form a ring.

Examples of the ring formed include the ring R. Preferred examplesinclude, but are not limited to, the followings. Also, the followingscan be used in any combination.

-   -   A case where R₁ and R₂ are combined to form a carbazole ring        together with the nitrogen atom to which R₁ and R₂ are bonded.    -   A case where R₅ and R₆ are combined to form a benzene ring or a        dioxane ring (in this case, the ring combines with the thiophene        ring formed by combining R₅ and R₆, to form a        3,4-ethylenedioxythiophene ring).    -   A case where m is 1 or more and where R₃ and R₅ are combined to        form a benzene ring or where either R₃ or R₅ is a sulfur        atom-containing group and these members are combined to form a        thiophene ring.    -   A case where n is 1 or more and where R₆ and R₈ are combined to        form a benzene ring or where either R₆ or R₈ is a sulfur        atom-containing group and these members are combined to form a        thiophene ring.    -   A case where m is 2 or more and where a pair of R₃ and R₅ and a        pair of R₃ and R₃′ each is combined to form a naphthalene ring        or where either R₃ or R₅ and either R₃ or R₃′ are a sulfur        atom-containing group and each pair is combined to form a        benzothiophene ring.    -   A case where n is 2 or more and where a pair of R₆ and R₈ and a        pair of R₈ and R₈′ each is combined to form a naphthalene ring        or where either R₆ or R₈ and either R₈ or R₈′ are a sulfur        atom-containing group and each pair is combined to form a        benzothiophene ring.

Examples of the ring formed by R₁₀ and R₁₁ include 1,3-indandione,1,3-benzindandione, 1,3-cyclohexanedione,5,5-dimethyl-1,3-cyclohexanedione, 1,3-dioxane-4,6-dione,1-phenyl-2-pyrazolin-5-one, 3-methyl-1-phenyl-2-pyrazolin-5-one,1-(2-benzothiazoyl)-3-methyl-2-pyrazolin-5-one andpyrimidine-2,4,6-trione.

The compound represented by formula (1) is preferably a compoundrepresented by the following formula (2).

wherein R₁ to R₉, m and n have the same meanings as above, each of R₁₁and R₁₂ independently represents a hydrogen atom or a substituent, andR₁₁ and R₁₂ may combine with each other to form a ring.

In the case of forming a ring by R₁₁ and R₁₂, examples of the ringinclude those of the ring formed by R₁₀ and R₁₁.

The compound represented by formula (2) is preferably a compoundrepresented by the following formula (3).

wherein R₁ to R₉, m and n have the same meanings as above, each of R₁₃and R₁₄ independently represents a hydrogen atom or a substituent, andR₁₃ and R₁₄ may combine with each other to form a ring.

In the case of forming a ring by R₁₃ and R₁₄, examples of the ringinclude the ring R. Among these, a benzene ring, a naphthalene ring andan anthracene ring are preferred.

The compound represented by formula (3) is preferably a compoundrepresented by the following formula (4) or a compound represented bythe following formula (5).

(wherein R₁ to R₉, m and n have the same meanings as above, each of R₁₅to R₁₈ independently represents a hydrogen atom or a substituent, andR₁₅ and R₁₆, R₁₆ and R₁₇, or R₁₇ and R₁₈ may be combined with each otherto form a ring).

(wherein R₁ to R₉, m and n have the same meanings as above, each of R₁₅and R₁₈ to R₂₂ independently represents a hydrogen atom or asubstituent, and R₁₅ and R₁₉, R₁₉ and R₂₀, R₂₀ and R₂₁, R₂₁ and R₂₂, orR₂₂ and R₁₈ may be combined with each other to form a ring).

In formulae (4) and (5), each of R₁₅ to R₂₂ is preferably a hydrogenatom, a halogen atom, an alkyl group having a carbon number of 1 to 10,an aryl group having a carbon number of 6 to 20, or a heteroaryl groupcomposed of a 5-, 6- or 7-membered ring or a condensed ring thereof,containing at least any one of oxygen atom, sulfur atom and nitrogenatom as a heteroatom, more preferably a hydrogen atom, a fluorine atom,an alkyl group having a carbon number of 1 to 10, or an aryl grouphaving a carbon number of 6 to 20.

The compound represented by formula (4) and the compound represented byformula (5) are novel compounds not found in literatures and are usefulparticularly as a photoelectric conversion material used in photosensorsand photocells. Also, as other applications, the compounds can be used,for example, as a coloring material, a liquid crystal material, anorganic semiconductor material, an organic luminescence device material,a charge transport material, a medical material, and a fluorescentdiagnostic agent material.

The compounds represented by formulae (1) to (5) can be synthesized, forexample, according to the following reactions (when the startingmaterial dibromothiophene derivative is symmetric).

Each reaction above can be performed by referring to a known synthesistechnique. The synthesis of an aldehyde form from a bromo form can beperformed by referring to J. Org. Chem., 2000, 65, 9120. The reactionwith amine is known as a Buchwald-Hartwig reaction (see, Org. Synth.,2004, 10, 423, and Org. Synth., 2002, 78, 23). The reaction of analdehyde form and 1,3-diketone is known as Knoevenagel condensationreaction (see, Ber. Deutsch. Chem. Ges., 1898, 31, 2596). The reactionof an aldehyde form and a monoketone is known as aldol condensationreaction (see, J. Am. Chem. Soc., 1979, 101, 1284).

In the case where the starting material is asymmetric (when m≧1 andn=0), the compounds can be synthesized according to the followingreaction.

SMEAH: Sodium bis(2-methoxyethoxy)aluminum hydride

The starting compound can be synthesized according to the methoddescribed in J. Med. Chem., 2007, 50, 4793. The reduction reaction froman ester form to an aldehyde form can be performed by referring toSynthesis, 2003, 822.

Furthermore, when m=0 and the compounds can be synthesized according tothe following reaction.

The starting compound can be synthesized by the method described in J.Med. Chem., 2003, 46, 2446. The bromination using NBS(N-bromosuccinimide) can be performed by referring to Tetrahedron, 2001,17, 3785.

Also, when n is 2 or more and a ring is formed by R₇ and R₈′, thecompounds can be synthesized according to the following reaction.

The coupling reaction of a bromo form and boric acid is known asSuzuki-Miyaura coupling reaction (see, Tetrahedron Lett., 1979, 3437).

In the formulae, R₁, R₂, R₅, R₆, R₁₁ and R₁₂ have the same meanings asabove.

The compound represented by formula (5) is preferably a compoundrepresented by the following formula (11) or the following formula (12).

wherein R₁, R₂, R₅, R₆, R₉, R₁₅ and R₁₈ to R₂₂ have the same meanings asabove, and preferred ranges are also the same.

wherein R₁, R₂, R₅, R₇, R₉, R₁₅ and R₁₈ to R₂₂ have the same meanings asabove, and preferred ranges are also the same.

(Molecular Weight)

In view of suitability for film production, the molecular weight of thecompounds represented by formula (1) is preferably from 300 to 1,500,more preferably from 350 to 1,200, still more preferably from 400 to900. If the molecular weight is too small, the thickness of thephotoelectric conversion film deposited is reduced due tovolatilization, whereas if the molecular weight is excessively large,the compound cannot be vapor-deposited and a photoelectric conversiondevice cannot be fabricated.

(Melting Point)

In view of deposition stability, the melting point of the compoundrepresented by formula (1) is preferably 200° C. or more, morepreferably 250° C. or more, still more preferably 280° C. or more. Ifthe melting point is low, the compound melts out before vapordeposition, making it impossible to stably deposit a film, and inaddition, the decomposition product of the compound increases todeteriorate the photoelectric conversion performance.

(Absorption Spectrum)

From the standpoint of broadly absorbing light in the visible region,the peak wavelength in the absorption spectrum of the compoundrepresented by formula (1) is preferably from 450 to 700 nm, morepreferably from 480 to 700 nm, still more preferably from 510 to 680 nm.

(Molar Extinction Coefficient of Peak Wavelength)

From the standpoint of efficiently utilizing light, the molar extinctioncoefficient of the compound represented by formula (1) is preferablyhigher and is preferably 30,000 M⁻¹ cm⁻¹ or more, more preferably 50,000M⁻¹ cm⁻¹ or more, still more preferably 70,000 M⁻¹ cm⁻¹ or more.

Specific examples of the compound represented by formula (1) areillustrated below, but the present invention is not limited thereto.

The photoelectric conversion layer 12 contains an n-type organicsemiconductor.

The n-type organic semiconductor is an acceptor-type organicsemiconductor and indicates an organic compound having a property ofreadily accepting an electron, mainly typified by anelectron-transporting organic compound. More specifically, this is anorganic compound having a larger electron affinity when two organiccompounds are used in contact. Accordingly, for the acceptor-typeorganic compound, any organic compound can be used as long as it is anorganic compound having an electron accepting property. Examples thereofinclude a fullerene derivative, a fused aromatic carbocyclic compound (anaphthalene derivative, an anthracene derivative, a phenanthrenederivative, a tetracene derivative, a pyrene derivative, a perylenederivative and a fluoranthene derivative), a 5- to 7-memberedheterocyclic compound containing nitrogen atom, oxygen atom or sulfuratom (e.g., pyridine, pyrazine, pyrimidine, pyridazine, triazine,quinoline, quinoxaline, quinazoline, phthalazine, cinnoline,isoquinoline, pteridine, acridine, phenazine, phenanthroline, tetrazole,pyrazole, imidazole, thiazole, oxazole, indazole, benzimidazole,benzotriazole, benzoxazole, benzothiazole, carbazole, purine,triazolopyridazine, triazolopyrimidine, tetrazaindene, oxadiazole,imidazopyridine, pyralidine, pyrrolopyridine, thiadiazolopyridine,dibenzazepine, tribenzazepine), a polyarylene compound, a fluorenecompound, a cyclopentadiene compound, a silyl compound, and a metalcomplex having a nitrogen-containing heterocyclic compound as a ligand.

The fullerene indicates fullerene C₆₀, fullerene C₇₀, fullerene C₇₆,fullerene C₇₈, fullerene C₈₀, fullerene C₈₂, fullerene C₈₄, fullereneC₉₀, fullerene C₉₆, fullerene C₂₄₀, fullerene C₅₄₀, a mixed fullerene ora fullerene nanotube, and the fullerene derivative indicates a compoundobtained by adding a substituent to such a fullerene. The substituent ispreferably an alkyl group, an aryl group or a heterocyclic group.

The compounds described in JP-A-2007-123707 are preferred as thefullerene derivative.

As for the fullerene and fullerene derivative, the compounds described,for example, in Kikan Kagaku Sosetsu (Scientific Review Quarterly), No.43, edited by The Chemical Society of Japan (1999), JP-A-10-167994,JP-A-11-255508, JP-A-11-255509, JP-A-2002-241323 and JP-A-2003-196881may also be used.

Out of a fullerene and a fullerene derivative, a fullerene is preferred,and fullerene C₆₀ is more preferred.

The photoelectric conversion layer preferably has a bulk heterojunctionstructure formed in a state of the compound represented by formula (1)and a fullerene or a fullerene derivative being mixed. Theheterojunction structure contained therein compensates for a drawbackthat the carrier diffusion length in the photoelectric conversion layeris short, whereby the photoelectric conversion efficiency of thephotoelectric conversion layer can be enhanced. Incidentally, the bulkheterojunction structure is described in detail, for example, inJP-A-2005-303266, paragraphs [0013] and [0014].

The volume ratio of the fullerene or fullerene derivative to thecompound represented by formula (1) (fullerene or fullerenederivative/compound represented by formula (1)×100(%)) is preferably 50%or more, more preferably from 80 to 1,000% (volume ratio), still morepreferably from 100 to 700% (volume ratio).

The photoelectric conversion layer can be deposited by a dry depositionmethod or a wet deposition method. Specific examples of the drydeposition method include a physical vapor growth method such as vacuumdeposition method, sputtering method, ion plating method and MBE method,and a CVD method such as plasma polymerization. As for the wetdeposition method, a cast method, a spin coating method, a dippingmethod, an LB method and the like are used. A dry deposition method ispreferred, and a vacuum deposition method is more preferred. In the caseof depositing the layer by a vacuum deposition method, the productionconditions such as vacuum degree and vapor deposition temperature can beset in accordance with conventional methods.

The thickness of the photoelectric conversion layer is preferably from10 to 1,000 nm, more preferably from 50 to 800 nm, still more preferablyfrom 100 to 500 nm. With a thickness of 10 nm or more, a suitable effectof suppressing a dark current is obtained, and with a thickness of 1,000nm or less, a suitable photoelectric conversion efficiency is obtained.

(Electron Blocking Layer)

For the electron blocking layer, an electron-donating organic materialcan be used. Specifically, examples of the low molecular material whichcan be used include an aromatic diamine compound such asN,N-bis(3-methylphenyl)-(1,1′-biphenyl)-4,4′-diamine (TPD) and4,4′-bis[N-(naphthyl)-N-phenylamino]biphenyl (α-NPD), oxazole,oxadiazole, triazole, imidazole, imidazolone, a stilbene derivative, apyrazolone derivative, tetrahydroimidazole, a polyarylalkane, butadiene,4,4′,4″-tris(N-(3-methylphenyl)N-phenylamino)triphenylamine (m-MTDATA),a porphyrin compound such as porphin, copper tetraphenylporphin,phthalocyanine, copper phthalocyanine and titanium phthalocyanine oxide,a triazole derivative, an oxadiazole derivative, an imidazolederivative, a polyarylalkane derivative, a pyrazoline derivative, apyrazolone derivative, a phenylenediamine derivative, an anilaminederivative, an amino-substituted chalcone derivative, an oxazolederivative, a styrylanthracene derivative, a fluorenone derivative, ahydrazone derivative, and a silazane derivative. As for the polymermaterial, a polymer such as phenylenevinylene, fluorene, carbazole,indole, pyrene, pyrrole, picolin, thiophene, acetylene and diacetylene,or a derivative thereof may be used. A compound having a sufficient holetransportability may be used even if it is not an electron-donatingcompound.

Specifically, the compounds described in JP-A-2008-72090, paragraphs[0083] to

are preferred.

(Hole Blocking Layer)

For the hole-blocking layer, an electron-accepting organic material canbe used.

Examples of the electron-accepting material which can be used include anoxadiazole derivative such as1,3-bis(4-tert-butylphenyl-1,3,4-oxadiazolyl)phenylene (OXD-7); ananthraquinodimethane derivative; a diphenylquinone derivative; abathocuproine, a bathophenanthroline and a derivative thereof; atriazole compound; a tris(8-hydroxyquinolinato)aluminum complex; abis(4-methyl-8-quinolinato)aluminum complex; a distyrylarylenederivative; and a silole compound. Also, a material having sufficientelectron transportability may be used even if it is not anelectron-accepting organic material. A porphyrin-based compound, astyryl-based compound such as DCM(4-dicyanomethylene-2-methyl-6-(4-(dimethylaminostyryl))-4H pyran), anda 4H pyran-based compound can be used. Specifically, the compoundsdescribed in JP-A-2008-72090, paragraphs [0073] to [0078] are preferred.

The thickness of the electron blocking layer/hole blocking layer ispreferably from 10 to 200 nm, more preferably from 30 to 150 nm, stillmore preferably from 50 to 100 nm, because if this thickness is toosmall, the effect of suppressing a dark current is decreased, whereas ifthe thickness is excessively large, the photoelectric conversionefficiency is deteriorated.

[Photosensor]

The photoelectric conversion device is roughly classified into aphotocell and a photo sensor, and the photoelectric conversion device ofthe present invention is suited for a photosensor. The photosensor maybe a photosensor using the above-described photoelectric conversiondevice alone or may be in the mode of a line sensor where thephotoelectric conversion devices are linearly arranged, or atwo-dimensional sensor where the photoelectric conversion devices arearranged on a plane. The photoelectric conversion device of the presentinvention functions as an imaging device, in the line sensor, byconverting the optical image information into electric signals with useof an optical system and a drive part like, for example, a scanner and,in the two-dimensional sensor, by forming an image of optical imageinformation on a sensor by means of an optical system and converting itinto electric signals like an imaging module.

The photocell is a power generating unit and therefore, the efficiencyof converting light energy into electric energy is an importantperformance, but the dark current that is a current in a dark place doesnot become a problem in function. Furthermore, a heating step in thelater stage, such as placement of a color filter, is not required. Inthe photosensor, high-precision conversion of light/dark signals intoelectric signals is an important performance and in turn, the efficiencyof converting light quantity into a current is also an importantperformance. Moreover, a signal when output in a dark place works out toa noise and therefore, low dark current is required. Furthermore, theresistance to a step in the later sage is also important.

[Imaging Device]

Configuration examples of an imaging device equipped with thephotoelectric conversion device are described below. In the followingconfiguration examples, the members and the like having the sameconfiguration/action as the members described above are indicated by thesame or like symbols or numerical references in the figure, and theirdescription is simplified or omitted.

The imaging device is a device of converting optical information of animage into electric signals, where a plurality of photoelectricconversion devices are arranged in the same plane on a matrix and wherelight signals can be converted into electric signals in eachphotoelectric conversion device (pixel) and each pixel can sequentiallyoutput the electric signals to the outside of the imaging device.Therefore, the imaging device has one photoelectric conversion deviceand one or more transistors per one pixel.

(First Configuration Example of Imaging Device)

FIG. 2 is a schematic cross-sectional view of one pixel portion of animaging device.

In the imaging device 100, a large number of pixels each constitutingone pixel are disposed in an array manner in the same plane, andone-pixel data of the image data can be produced by the signals obtainedfrom the one pixel.

One pixel of the imaging device shown in FIG. 2 is composed of an n-typesilicon substrate 1, a transparent insulating film 7 formed on then-type silicon substrate 1, and a photoelectric conversion deviceconsisting of a lower electrode 101 formed on the insulating film 7, aphotoelectric conversion layer 102 formed on the lower electrode 101 anda transparent electrode material-containing upper electrode 104 formedon the photoelectric conversion layer 102. A light-shielding film 14having provided therein an opening is formed on the photoelectricconversion device, and a transparent insulating film 15 is formed on theupper electrode 104.

Inside the n-type silicon substrate 1, a p-type impurity region(hereinafter simply referred to as “p region”) 4, an n-type impurityregion (hereinafter simply referred to as “n region”) 3, and a p region2 are formed in order of increasing the depth. In the p region 4, ahigh-concentration p region 6 is formed in the surface part of theportion light-shielded by the light-shielding film 14, and the p region6 is surrounded by an n region 5.

The depth of the pn junction plane between the p region 4 and the nregion 3 from the surface of the n-type silicon substrate 1 is set to adepth at which blue light is absorbed (about 0.2 μm). Therefore, the pregion 4 and the n region 3 form a photodiode (B photodiode) ofabsorbing blue light and accordingly accumulating electric charges.

The depth of the pn junction plane between the p region 2 and the n-typesilicon substrate 1 from the surface of the n-type silicon substrate 1is set to a depth at which red light is absorbed (about 2 μm).Therefore, the p region 2 and the n-type silicon substrate 1 form aphotodiode (R photodiode) of absorbing red light and accordinglyaccumulating electric charges.

The p region 6 is electrically connected to the lower electrode 101 viaa connection part 9 formed in the opening bored through the insulatingfilm 7. A hole trapped by the lower electrode 101 recombines with anelectron in the p region 6 and therefore, the number of electronsaccumulated in the p region 6 on resetting decreases according to thenumber of holes trapped. The connection part 9 is electrically insulatedby an insulating film 8 from portions except for the lower electrode 101and the p region 6.

The electrons accumulated in the p region 2 are converted into signalsaccording to the electric charge amount by an MOS circuit (not shown)composed of a p-channel MOS transistor formed inside the n-type siliconsubstrate 1, the electrons accumulated in the p region 4 are convertedinto signals according to the electric charge amount by an MOS circuit(not shown) composed of a p-channel MOS transistor formed inside the nregion 3, the electrons accumulated in the p region 6 are converted intosignals according to the electric charge amount by an MOS circuit (notshown) composed of a p-channel MOS transistor formed inside the n region5, and these signals are output to the outside of the imaging device100. Each MOS circuit is connected to a signal read-out pad (not shown)by a wiring 10. Incidentally, when an extractor electrode is provided inthe p region 2 and p region 4 and a predetermined reset potential isapplied, each region is depleted and the capacitance of each pn junctionpart becomes an infinitely small value, whereby the capacitance producedin the junction plane can be made extremely small.

Thanks to such a configuration, G light can be photoelectricallyconverted by the photoelectric conversion layer 102, and B light and Rlight can be photoelectrically converted by the B photodiode and the Rphotodiode, respectively, in the n-type silicon substrate 1. Also, sinceG light is first absorbed in the upper part, excellent color separationis achieved between B-G and between G-R. This is a greatly excellentpoint in comparison with an imaging device of the type where three PDare stacked inside a silicon substrate and all of BGR lights areseparated inside the silicon substrate.

(Second Configuration Example of Imaging Device)

In this embodiment, instead of a configuration where two photodiodes arestacked inside a silicon substrate 1 as in the imaging device of FIG. 2,two photodiodes are arrayed in the direction perpendicular to theincident direction of incident light so that lights of two colors can bedetected in the inside of the p-type silicon substrate.

FIG. 3 is a schematic cross-sectional view of one pixel portion of animaging device of this configuration example.

One pixel of the imaging device 200 shown in FIG. 3 is composed of ann-type silicon substrate 17 and a photoelectric conversion deviceconsisting of a lower electrode 101 formed above the n-type siliconsubstrate 17, a photoelectric conversion layer 102 formed on the lowerelectrode 101, and an upper electrode 104 formed on the photoelectricconversion layer 102. A light-shielding film 34 having provided thereinan opening is formed on the photoelectric conversion device, and atransparent insulating film 33 is formed on the upper electrode 104.

On the surface of the n-type silicon substrate 17 below the opening ofthe light-shielding film 34, a photodiode consisting of an n region 19and a p region 18 and a photodiode consisting of an n region 21 and a pregion 20 are formed to lie in juxtaposition on the surface of then-type silicon substrate 17. An arbitrary plane direction on the n-typesilicon substrate 17 surface becomes the direction perpendicular to theincident direction of incident light.

Above the photodiode consisting of an n region 19 and a p region 18, acolor filter 28 capable of transmitting B light is formed via atransparent insulating film 24, and the lower electrode 101 is formedthereon. Above the photodiode consisting of an n region 21 and a pregion 20, a color filter 29 capable of transmitting R light is formedvia the transparent insulating film 24, and the lower electrode 101 isformed thereon. The peripheries of color filters 28 and 29 are coveredwith a transparent insulating film 25.

The photodiode consisting of an n region 19 and a p region 18 functionsas an in-substrate photoelectric conversion part that absorbs B lighttransmitted through the color filter 28, accordingly generates electronsand accumulates the generated electrons in the p region 18. Thephotodiode consisting of an n region 21 and a p region 20 functions asan in-substrate photoelectric conversion part that absorbs R lighttransmitted through the color filter 29, accordingly generates electronsand accumulates the generated holes in the p region 20.

In the portion light-shielded by the light-shielding film 34 on then-type silicon substrate 17 surface, a p region 23 is formed, and theperiphery of the p region 23 is surrounded by an n region 22.

The p region 23 is electrically connected to the lower electrode 101 viaa connection part 27 formed in the opening bored through the insulatingfilms 24 and 25. A hole trapped by the lower electrode 101 recombineswith an electron in the p region 23 and therefore, the number ofelectrons accumulated in the p region 23 on resetting decreasesaccording to the number of holes trapped. The connection part 27 iselectrically insulated by an insulating film 26 from portions except forthe lower electrode 101 and the p region 23.

The electrons accumulated in the p region 18 are converted into signalsaccording to the electric charge amount by an MOS circuit (not shown)composed of a p-channel MOS transistor formed inside the n-type siliconsubstrate 17, the electrons accumulated in the p region 20 are convertedinto signals according to the electric charge amount by an MOS circuit(not shown) composed of a p-channel MOS transistor formed inside then-type silicon substrate 17, the electrons accumulated in the p region23 are converted into signals according to the electric charge amount byan MOS circuit (not shown) composed of an n-channel MOS transistorformed inside the n region 22, and these signals are output to theoutside of the imaging device 200. Each MOS circuit is connected to asignal read-out pad (not shown) by a wiring 35.

In this connection, instead of MOS circuits, the signal read-out partmay be composed of CCD and an amplifier, that is, may be a signalread-out part where electrons accumulated in the p region 18, p region20 and p region 23 are read out into CCD formed inside the n-typesilicon substrate 17 and then transferred to an amplifier by the CCD andsignals according to the electrons transferred are output from theamplifier.

In this way, the signal read-out part includes a CCD structure and aCMOS structure, but in view of power consumption, high-speed read-out,pixel addition, partial read-out and the like, CMOS is preferred.

Incidentally, in the imaging device of FIG. 3, color separation of Rlight and B light is performed by color filters 28 and 29, but insteadof providing color filters 28 and 29, the depth of the pn junction planebetween the p region 20 and the n region 21 and the depth of the pnjunction plane between the p region 18 and the n region 19 each may beadjusted to absorb R light and B light by respective photodiodes.

An inorganic photoelectric conversion part composed of an inorganicmaterial that absorbs light transmitted through the photoelectricconversion layer 102, accordingly generates electric charges andaccumulates the electric charges, may also be formed between the n-typesilicon substrate 17 and the lower electrode 101 (for example, betweenthe insulating film 24 and the n-type silicon substrate 17). In thiscase, an MOS circuit for reading out signals according to the electriccharges accumulated in a charge accumulation region of the inorganicphotoelectric conversion part may be provided inside the n-type siliconsubstrate 17, and a wiring 35 may be connected also to this MOS circuit.

Also, there may take a configuration where one photodiode is providedinside the n-type silicone substrate 17 and a plurality of photoelectricconversion parts are stacked above the n-type silicon substrate 17; aconfiguration where a plurality of photodiodes are provided inside then-type silicon substrate 17 and a plurality of photoelectric conversionparts are stacked above the n-type silicon substrate 17; or when a colorimage need not be formed, a configuration where one photodiode isprovided inside the n-type silicon substrate 17 and only onephotoelectric conversion part is stacked.

(Third Configuration Example of Imaging Device)

The imaging device of this embodiment has a configuration where aphotodiode is not provided inside the silicon substrate and a pluralityof (here, three) photoelectric conversion devices are stacked above thesilicon substrate.

FIG. 4 is a schematic cross-sectional view of one pixel portion of theimaging device of this configuration example.

The imaging device 300 shown in FIG. 4 has a configuration where an Rphotoelectric conversion device, a B photoelectric conversion device,and a G photoelectric conversion device are stacked in order above asilicon substrate 41.

The R photoelectric conversion device is composed of, above the siliconsubstrate 41, a lower electrode 101 r, a photoelectric conversion layer102 r formed on the lower electrode 101 r, and an upper electrode 104 rformed on the photoelectric conversion layer 102 r.

The B photoelectric conversion device is composed of a lower electrode101 b stacked on the upper electrode 104 r of the R photoelectricconversion device, a photoelectric conversion layer 102 b formed on thelower electrode 101 b, and an upper electrode 104 b formed on thephotoelectric conversion layer 102 b.

The G photoelectric conversion device is composed of a lower electrode101 g stacked on the upper electrode 104 b of the B photoelectricconversion device, a photoelectric conversion layer 102 g formed on thelower electrode 101 g, and an upper electrode 104 g formed on thephotoelectric conversion layer 102 g. The imaging device of thisconfiguration example has a configuration where the R photoelectricconversion device, the B photoelectric conversion device and the Gphotoelectric conversion device are stacked in this order.

A transparent insulating film 59 is formed between the upper electrode104 r of the R photoelectric conversion device and the lower electrode101 b of the B photoelectric conversion device, and a transparentinsulating film 63 is formed between the upper electrode 104 b of the Bphotoelectric conversion device and the lower electrode 101 g of the Gphotoelectric conversion device. A light-shielding film 68 is formed inthe region excluding an opening on the upper electrode 104 g of the Gphotoelectric conversion device, and a transparent insulating film 67 isformed to cover the upper electrode 104 g and the light-shielding film68.

The lower electrode, the photoelectric conversion layer and the upperelectrode contained in each of the R, G and B photoelectric conversiondevices can have the same configuration as that in the photoelectricconversion device described above. However, the photoelectric conversionlayer 102 g contains an organic material capable of absorbing greenlight and accordingly generating electrons and holes, the photoelectricconversion layer 102 b contains an organic material capable of absorbingblue light and accordingly generating electrons and holes, and thephotoelectric conversion layer 102 r contains an organic materialcapable of absorbing red light and accordingly generating electrons andholes.

In the portion light-shielded by the light-shielding film 68 on thesilicon substrate 41 surface, p regions 43, 45 and 47 are formed, andthe peripheries of these regions are surrounded by n regions 42, 44 and46, respectively.

The p region 43 is electrically connected to the lower electrode 101 rvia a connection part 54 formed in an opening bored through aninsulating film 48. A hole trapped by the lower electrode 101 rrecombines with an electron in the p region 43 and therefore, the numberof electrons accumulated in the p region 43 on resetting decreasesaccording to the number of holes trapped. The connection part 54 iselectrically insulated by an insulating film 51 from portions except forthe lower electrode 101 r and the p region 43.

The p region 45 is electrically connected to the lower electrode 101 bvia a connection part 53 formed in an opening bored through theinsulating film 48, the R photoelectric conversion device and theinsulating film 59. A hole trapped by the lower electrode 101 brecombines with an electron in the p region 45 and therefore, the numberof electrons accumulated in the p region 45 on resetting decreasesaccording to the number of holes trapped. The connection part 53 iselectrically insulated by an insulating film 50 from portions except forthe lower electrode 101 b and the p region 45.

The p region 47 is electrically connected to the lower electrode 101 gvia a connection part 52 formed in an opening bored through theinsulating film 48, the R photoelectric conversion device, theinsulating film 59, the B photoelectric conversion device and theinsulating film 63. A hole trapped by the lower electrode 101 grecombines with an electron in the p region 47 and therefore, the numberof electrons accumulated in the p region 47 on resetting decreasesaccording to the number of holes trapped. The connection part 52 iselectrically insulated by an insulating film 49 from portions except forthe lower electrode 101 g and the p region 47.

The electrons accumulated in the p region 43 are converted into signalsaccording to the electric charge amount by an MOS circuit (not shown)composed of a p-channel MOS transistor formed inside the n region 42,the electrons accumulated in the p region 45 are converted into signalsaccording to the electric charge amount by an MOS circuit (not shown)composed of a p-channel MOS transistor formed inside the n region 44,the electrons accumulated in the p region 47 are converted into signalsaccording to the electric charge amount by an MOS circuit (not shown)composed of a p-channel MOS transistor formed inside the n region 46,and these signals are output to the outside of the imaging device 300.Each MOS circuit is connected to a signal read-out pad (not shown) by awiring 55. Incidentally, instead of MOS circuits, the signal read-outpart may be composed of CCD and an amplifier, that is, may be a signalread-out part where electrons accumulated in the p regions 43, 45 and 47are read out into CCD formed inside the silicon substrate 41 and thentransferred to an amplifier by the CCD and signals according to theelectrons transferred are output from the amplifier.

In the description above, the photoelectric conversion layer capable ofabsorbing B light means a layer which can absorb at least light at awavelength of 400 to 500 nm and in which the absorption factor at a peakwavelength in the wavelength region above is preferably 50% or more. Thephotoelectric conversion layer capable of absorbing G light means alayer which can absorb at least light at a wavelength of 500 to 600 nmand in which the absorption factor at a peak wavelength in thewavelength region above is preferably 50% or more. The photoelectricconversion layer capable of absorbing R light means a layer which canabsorb at least light at a wavelength of 600 to 700 nm and in which theabsorption factor at a peak wavelength in the wavelength region above ispreferably 50% or more.

(Fourth Configuration Example of Imaging Device)

FIG. 5 is a schematic partial surface view of an imaging device fordescribing the embodiment of the present invention. FIG. 6 is aschematic cross-sectional view cut along the A-A line of the imagingdevice shown in FIG. 5.

A p-well layer 402 is formed on an n-type silicon substrate 401. In thefollowing, the n-type silicon substrate 401 and the p-well layer 402 arecollectively referred to as a semiconductor substrate. In the rowdirection and the column direction crossing with the row direction atright angles in the same plane above the semiconductor substrate, threekinds of color filters, that is, a color filter 413 r mainlytransmitting R light, a color filter 413 g mainly transmitting G light,and a color filter 413 b mainly transmitting B light, each is numerouslyarrayed.

As for the color filter 413 r, a known material may be used, but thematerial transmits R light. As for the color filter 413 g, a knownmaterial may be used, but the material transmits G light. As for thecolor filter 413 b, a known material may be used, but the materialtransmits B light.

As for the array of color filters 413 r, 413 g and 413 b, a color filterarray used in known single-plate solid-state imaging devices (e.g.,Bayer array, longitudinal stripe, lateral stripe) may be employed.

A transparent electrode 411 r is formed above an n region 404 r, atransparent electrode 411 g is formed above an n region 404 g, and atransparent electrode 411 b is formed above an n region 404 b. Thetransparent electrodes 411 r, 411 g and 411 b are divided to correspondto the color filters 413 r, 413 g and 413 b, respectively. Thetransparent electrodes 411 r, 411 g and 411 b each has the same functionas the lower electrode 11 of FIG. 1.

A photoelectric conversion film 412 in one-sheet configuration shared incommon among the color filters 413 r, 413 g and 413 b is formed on thetransparent electrodes 411 r, 411 g and 411 b.

An upper electrode 413 in one-sheet configuration shared in common amongthe color filters 413 r, 413 g and 413 b is formed on the photoelectricconversion film 412.

A photoelectric conversion device corresponding to the color filter 413r is formed by the transparent electrode 411 r, the upper electrode 413opposing it, and a part of the photoelectric conversion film 412sandwiched therebetween. This photoelectric conversion device ishereinafter referred to as an R photoelectric conversion device, becausethis device is formed on a semiconductor substrate.

A photoelectric conversion device corresponding to the color filter 413g is formed by the transparent electrode 411 g, the upper electrode 413opposing it, and a part of the photoelectric conversion film 412sandwiched therebetween. This photoelectric conversion device ishereinafter referred to as a G photoelectric conversion device.

A photoelectric conversion device corresponding to the color filter 413b is formed by the transparent electrode 411 b, the upper electrode 413opposing it, and a part of the photoelectric conversion film 412sandwiched therebetween. This photoelectric conversion device ishereinafter referred to as a B photoelectric conversion device.

In the n region inside the p-well layer 402, a high-concentration n-typeimpurity region (hereinafter referred to as an “n+ region”) 404 r foraccumulating an electric charge generated in the photoelectricconversion film 412 of the on-substrate R photoelectric conversiondevice is formed. Incidentally, a light-shielding film is preferablyprovided on the n+ region 404 r for preventing light from entering then+ region 404 r.

In the n region inside the p-well layer 402, an n+ region 404 g foraccumulating an electric charge generated in the photoelectricconversion film 412 of the on-substrate G photoelectric conversiondevice is formed. Incidentally, a light-shielding film is preferablyprovided on the n+ region 404 g for preventing light from entering then+ region 404 g.

In the n region inside the p-well layer 402, an n+ region 404 b foraccumulating an electric charge generated in the photoelectricconversion film 412 of the on-substrate B photoelectric conversiondevice is formed. Incidentally, a light-shielding film is preferablyprovided on the n+ region 404 b for preventing light from entering then+ region 404 b.

A contact part 406 r composed of a metal such as aluminum is formed onthe n+ region 404 r, the transparent electrode 411 r is formed on thecontact part 406 r, and the n+ region 404 r and the transparentelectrode 411 r are electrically connected by the contact part 406 r.The contact part 406 r is embedded in an insulating layer 405transparent to visible light and infrared light.

A contact part 406 g composed of a metal such as aluminum is formed onthe n+ region 404 g, the transparent electrode 411 g is formed on thecontact part 406 g, and the n+ region 404 g and the transparentelectrode 411 g are electrically connected by the contact part 406 g.The contact part 406 g is embedded in the insulating layer 405.

A contact part 406 b composed of a metal such as aluminum is formed onthe n+ region 404 b, the transparent electrode 411 b is formed on thecontact part 406 b, and the n+ region 404 b and the transparentelectrode 411 b are electrically connected by the contact part 406 b.The contact part 406 b is embedded in the insulating layer 405.

Inside the p-well layer 402, in the region other than those where the n+regions 404 r, 404 g and 404 b are formed, a signal read-out part 405 rfor reading out signals according to electric charges generated in the Rphotoelectric conversion device and accumulated in the n+ region 404 r,a signal read-out part 405 g for reading out signals according toelectric charges generated in the G photoelectric conversion device andaccumulated in the n+ region 404 g, and a signal read-out part 405 b forreading out signals according to electric charges generated in the Bphotoelectric conversion device and accumulated in the n+ region 404 bare formed. For each of the signal read-out parts 405 r, 405 g and 405b, a known configuration using a CCD or MOS circuit may be employed.

A two-layer structure of protective layers 415 and 416 for protectingthe on-substrate photoelectric conversion devices is formed on thephotoelectric conversion film 412, and color filters 413 r, 413 g and413 b are formed on the protective layer 416.

When a predetermined bias voltage is applied to the transparentelectrode 411 r and the upper electrode 413, electric charges generatedin the photoelectric conversion film 412 constituting the on-substrate Rphotoelectric conversion device move to the n+ region 404 r through thetransparent electrode 411 r and the contact part 406 r and areaccumulated therein. Signals according to electric charges accumulatedin the n+ region 404 r are read out by the signal read-out part 405 rand output to the outside of the imaging device 400.

Similarly, when a predetermined bias voltage is applied to thetransparent electrode 411 g and the upper electrode 413, electriccharges generated in the photoelectric conversion film 412 constitutingthe on-substrate G photoelectric conversion device move to the n+ region404 g through the transparent electrode 411 g and the contact part 406 gand are accumulated therein. Signals according to electric chargesaccumulated in the n+ region 404 g are read out by the signal read-outpart 405 g and output to the outside of the imaging device 400.

Also, similarly, when a predetermined bias voltage is applied to thetransparent electrode 411 b and the upper electrode 413, electriccharges generated in the photoelectric conversion film 412 constitutingthe on-substrate B photoelectric conversion device move to the n+ region404 b through the transparent electrode 411 b and the contact part 406 band are accumulated therein. Signals according to electric chargesaccumulated in the n+ region 404 b are read out by the signal read-outpart 405 b and output to the outside of the imaging device 400.

In this way, the imaging device 400 can output, to the outside, signalsof an R component according to electric charges generated in the Rphotoelectric conversion device, signals of a G component according toelectric charges generated in the G photoelectric conversion device, andsignals of a B component according to electric charges generated in theB photoelectric conversion device, whereby a color image can beobtained. Thanks to this mode, the photoelectric conversion part becomesthin, so that resolution can be enhanced and a false color can bereduced. Also, the aperture ratio can be made large irrespective of thelower circuit and therefore, high sensitivity can be achieved.Furthermore, a microlens can be omitted and this is effective inreducing the number of components.

In this embodiment, the organic photoelectric conversion film needs tohave a maximum absorption wavelength in the green light region and havean absorption region over the entire visible light, but this can bepreferably realized by the materials specified above of the presentinvention.

EXAMPLES

The present invention is described in greater detail below by referringto Examples, but the present invention is not limited to these Examples.

Example 1

(Synthesis of Compound 5a)

2,5-Dibromothiophene (produced by Tokyo Chemical Industry Co., Ltd.)(3.0 ml) was dissolved in 100 ml of dehydrated THF, and the solution wasadjusted to an inner temperature of −78° C. in a dry ice bath.Subsequently, 19.2 ml of n-BuLi was slowly added dropwise and after 5minutes, 5.1 ml of dehydrated DMF was gradually added dropwise.Thereafter, the dry ice bath was removed, and the inner temperature wasraised to room temperature. After adding 2 N HCl, extraction with ethylacetate was performed, and the oil layer was washed with 1 N HCl and aq.NaCl, then dried over sodium sulfate and filtered. The obtained reactionmixture was separated on a silica gel column (developing solution:AcOEt/n-Hexane=¼), and the solvent was distilled off to obtain 1.3 g ofCompound (5a).

(Synthesis of Compound 5b)

Compound (5a) (1.0 g), 1.8 g of diphenylamine (produced by TokyoChemical Industry Co., Ltd.), 3.4 g of cesium carbonate, 59 mg ofpalladium acetate and 0.34 g of triphenylphosphine were added to 17 mlof dehydrated xylene, and the mixture was refluxed for 5 hours. Theresulting reaction mixture was suction-filtered and after distilling offthe solvent, purified on a silica gel column (developing solvent:toluene). The solvent was removed by distillation to obtain 0.3 g ofCompound (5b).

(Synthesis of Compound (5))

Compound (5b) (250 mg) and 210 mg of benzindandione were added to 5 mlof ethanol, and the mixture was refluxed for 3 hours. The resultingreaction mixture was allowed to cool and then suction-filtered, and thefilter cake was dissolved in a small amount of chloroform,recrystallized from ethanol and then suction-filtered to obtain 199 mgof Compound (5). The compound was identified by ¹H-NMR.

<Identification of Compound (5)>

¹H-NMR (CDCl₃) δ: 6.49 (1H, d), 7.30-7.49 (10H, m), 7.58-7.64 (2H, m),7.75 (1H, br), 7.89 H, s), 8.00 (2H, m), 8.25 (1H, s), 8.32 (1H, s).

Molecular weight: 457.54

<Measurement of Melting Point>

The melting point of Compound (5) was measured using TG/DTA 6200 AST-2manufactured by SII NanoTechnology Inc. and found to be 311° C.

<Measurement of Absorption Spectrum and Molar Extinction Coefficient>

The absorption spectrum (in a chloroform solution) of Compound (5) wasmeasured using UV-2550 manufactured by Shimadzu Corporation, as aresult, the peak wavelength was 549 nm and the molar extinctioncoefficient at this wavelength was 88,000

<Fabrication of Photoelectric Conversion Device>

In the embodiment of FIG. 1A, amorphous ITO was deposited on a CMOSsubstrate by sputtering to a thickness of 30 nm and patterned byphotolithography so as to allow one pixel to be present for eachphotodiode (PD) on the CMOS substrate, thereby forming a pixelelectrode, EB-3 was then deposited by vacuum heating deposition to athickness of 100 nm, a layer formed by co-depositing Compound (5) andfullerene (C₆₀) to a thickness of 100 nm and 300 nm, respectively, interms of a single layer was deposited thereon by vacuum heatingdeposition to form a photoelectric conversion layer, and amorphous ITOas an upper electrode was further deposited by sputtering to a thicknessof 5 nm to form a transparent electrode. In this way, a solid-stateimaging device was fabricated. After forming an SiO film as a protectivelayer by heating vapor deposition on the upper electrode, an Al₂O₃ layerwas formed thereon by an ALCVD method. For all layers of thephotoelectric conversion layer 12, the vacuum deposition was performedat a vacuum degree of 4×10⁻⁴ Pa or less.

Example 2 Synthesis of Compound (8)

Compound (8) was synthesized by the same synthesis method as that forCompound (5) except for changing diphenylamine to 1,2′-dinaphthylamine(produced by Tokyo Chemical Industry Co., Ltd.).

<Fabrication of Photoelectric Conversion Device>

A solid-state imaging device was fabricated in the same manner as inExample 1 except for changing Compound (5) in the photoelectricconversion layer 12 to Compound (8).

Example 3 Synthesis of Compound (18)

Compound (18) was synthesized by the same synthesis method as that forCompound (5) by using 2,5-dibromothieno[3,2-b]thiophene (produced byTokyo Chemical Industry Co., Ltd.) as the starting material. Thecompound was identified by ¹H-NMR.

<Identification of Compound (18)>

¹H-NMR (CDCl₃) δ: 6.65 (1H, s), 7.26-7.43 (10H, m), 7.65 (2H, m), 8.00(1H, s), 8.07 (2H, m), 8.23 (111, br), 8.39 (2H, d).

Molecular weight: 513.63

<Measurement of Absorption Spectrum and Molar Extinction Coefficient>

The peak wavelength of the absorption spectrum and the molar extinctioncoefficient thereof were determined by the same operation as in Example1, as a result, the peak wavelength of the absorption spectrum was 536nm and the molar extinction coefficient at this wavelength was 94,000M⁻¹ cm⁻¹.

<Fabrication of Photoelectric Conversion Device>

A solid-state imaging device was fabricated in the same manner as inExample 1 except for changing Compound (5) in the photoelectricconversion layer 12 to Compound (18).

Example 4 Synthesis of Compound (19)

Compound (19) was synthesized by the same synthesis method as that forCompound (18) except for changing diphenylamine toN-phenyl-2-naphthylamine (produced by Tokyo Chemical Industry Co.,Ltd.).

<Fabrication of Photoelectric Conversion Device>

A solid-state imaging device was fabricated in the same manner as inExample 1 except for changing Compound (5) in the photoelectricconversion layer 12 to Compound (19).

Example 5 Synthesis of Compound (34)

Compound (34) was synthesized by the same synthesis method as that forCompound (5) except for changing diphenylamine toN-phenyl-2-naphthylamine (produced by Tokyo Chemical Industry Co., Ltd.)and changing benzindandione to sodium thiobarbiturate (produced by TokyoChemical Industry Co., Ltd.).

<Fabrication of Photoelectric Conversion Device>

A solid-state imaging device was fabricated in the same manner as inExample 1 except for changing Compound (5) in the photoelectricconversion layer 12 to Compound (34).

Comparative Example 1

A solid-state imaging device was fabricated in the same manner as inExample 1 except for changing the photoelectric conversion layer 12 to alayer formed by depositing Comparative Compound (1) alone to a thicknessof 100 nm.

Comparative Compound (1)

Comparative Example 2

Fabrication of a solid-state imaging device was attempted in the samemanner as in Comparative Example 1 except for changing ComparativeCompound (1) to Comparative Compound (2), but the vapor deposition ratewas not stabilized during deposition of the photoelectric conversionlayer, failing in forming the layer with the above-described thickness,and a solid-state imaging device could not be fabricated.

Comparative Compound (2):

Comparative Example 3

A solid-state imaging device was fabricated in the same manner as inComparative Example 1 except for changing Comparative Compound (1) toComparative Compound (3), as a result, the photoelectric conversionefficiency and the dark current could not be measured due tocrystallization of the photoelectric conversion film.

Comparative Compound (3):

The external quantum efficiency at the maximum sensitivity wavelengthwhen the dark current in each of the devices of Examples 1 to 5 andComparative Example 1 was 400 pA/cm² is shown in Table 1. Incidentally,at the time of measuring the photoelectric conversion performance ofeach device, an appropriate voltage was applied.

The molar extinction coefficient of the compound used in each of thedevices of Examples 1 to 5 and Comparative Example 1 was determined. Theresults are shown in Table 1.

TABLE 1 External Quantum Efficiency at Maximum Sensitivity WavelengthMolar Compound Used for with Extinction Light-Absorbing/ Dark CurrentCoefficient Photoelectric of 400 pA/cm² (relative Conversion Material(relative value) value) Example 1 Compound (5) and C₆₀ 100 94 Example 2Compound (8) and C₆₀ 100 95 Example 3 Compound (18) and C₆₀ 100 98Example 4 Compound (19) and C₆₀ 100 100 Example 5 Compound (34) and C₆₀98 70 Comparative Comparative Compound (1) <1 47 Example 1

As seen from Table 1, according to the present invention, a solid-stateimaging device having high photoelectric coefficient can be obtained.

The entire disclosure of Japanese Patent Application No. 2009-225522filed on Sep. 29, 2009, from which the benefit of foreign priority hasbeen claimed in the present application, is incorporated herein byreference, as if fully set forth.

What is claimed is:
 1. A compound represented by the following formula (4):

wherein each of R₁ and R₂ independently represents a substituted aryl group, an unsubstituted aryl group, a substituted heteroaryl group or an unsubstituted heteroaryl group, each of R₃ to R₉ and R₁₅ to R₁₈ independently represents a hydrogen atom or a substituent, m represents 0 or 1, and n represents an integer of 0 or more, R₁ and R₂, R₃ and R₄, R₃ and R₅, R₅ and R₆, R₆ and R₈, R₇ and R₈, R₇ and R₉, R₁₅ and R₁₆, R₁₆ and R₁₇, or R₁₇ and R₁₈ may be combined each other to form a ring, and when n is an integer of 2 or more, out of a plurality of R₇'s and R₈'s, a pair of R₇'s, a pair of R₈'s, or a pair of R₇ and R₈ may be combined each other to form a ring.
 2. A compound represented by the following formula (5):

wherein each of R₁ and R₂ independently represents a substituted aryl group, an unsubstituted aryl group, a substituted heteroaryl group or an unsubstituted heteroaryl group, each of R₃ to R₉, R₁₅ and R₁₈ to R₂₂ independently represents a hydrogen atom or a substituent, m represents 0 or 1, and n represents an integer of 0 or more, R₁ and R₂, R₃ and R₄, R₃ and R₅, R₅ and R₆, R₆ and R₈, R₇ and R₈, R₇ and R₉, R₁₅ and R₁₉, R₁₉ and R₂₀, R₂₀ and R₂₁, R₂₁ and R₂₂, or R₂₂ and R₁₈ may be combined each other to form a ring, and when n is an integer of 2 or more, out of a plurality of R₇'s and R₈'s, a pair of R₇'s, a pair of R₈'s, or a pair of R₇ and R₈ may be combined each other to form a ring.
 3. A photoelectric conversion device comprising an electrically conductive film, an organic photoelectric conversion film, and a transparent electrically conductive film, wherein the organic photoelectric conversion film contains the compound according to claim
 1. 4. A photosensor comprising the photoelectric conversion device according to claim
 3. 5. An imaging device containing the photoelectric conversion device according to claim
 3. 